The present invention relates to an antenna device according to the preamble of claim 1. The present invention also relates to an antenna assembly comprising at least one antenna device and another antenna device according to the preamble of claim 23.
The most common used antenna type for GPS applications is a microstrip antenna, a so called patch antenna. The main disadvantage with the microstrip antennas is relatively high manufacturing costs. Another disadvantage is that microstrip antennas have a high built-in height, due to the fact that they require an earth plane and an intermediate dielectric material.
Other types of antennas having circular polarisation characteristics, which are cheaper to produce, are some types of helix-antennas or double-loop antennas. The drawback with this type of antenna is that they cannot be compared to the patch antenna in terms of narrow bandwidth and antenna gain. Narrow bandwidth is a crucial requirement for a GPS antenna in order to reduce noise and interference e.g. from a cellular phone antenna near by.
The present invention seeks to provide an antenna device, especially for GPS applications, which is cheap to manufacture and has a narrow bandwidth compared to prior art antennas.
According to an aspect of the present invention, there is provided an antenna device as specified in claim 1.
The invention is also directed to an antenna assembly combining the antenna device with another antenna as specified in claim 23.
An advantage with the present invention is that the antenna device is cheap to manufacture.
Another advantage with the present invention is that the antenna device has a narrow bandwidth, suitable for GPS applications.
Still another advantage is that the present invention has a low built-in height compared to prior art antennas.
An advantage with an embodiment of the present invention having a reflector is that the antenna gain of the antenna device can be increased compared to an antenna device without a reflector.
An advantage with the antenna assembly is that the antenna device according to the present invention may easily be integrated with another antenna device, not affecting the height of the antenna assembly.